1. Field of the Invention:
The present invention relates to a cassette for use with an electrophotographic copying machine, a facsimile apparatus, a printer, or the like, and more particularly to a copy paper retaining cassette so designed to prevent skewed feeding of paper sheets therefrom.
The invention further relates to a cassette capable of storing a greater quantity of copy sheets--as of plain paper--than a conventional cassette for the same purpose.
Although the invention is described particularly with respect to its use with a copying machine, such description is by way of example only and no intention to specifically limit the invention to such use is either intended or should be implied.
2. Description of the Prior Art:
It is well known, in conjunction with copying machines, to provide a cassette for retaining a quantity of copy papers or sheets. The cassette is loaded into the machine at a predeterminately fixed position, the copy sheets being individually fed therefrom during each copying or printing operation. Since it is generally necessary to utilize variously sized copy sheets with a single machine, a quantity of each size sheet is typically stored in its own cassette exclusively arranged for the particular sheets to be retained therein. Often, the interior dimensions of the cassettes are arranged so as to be slightly larger than the corresponding dimensions of the copy sheets to be retained, and, as a consequence, uneven or irregular stacking and slippage of various portions of the stack within the retaining area of the cassette are common problems. In addition, normal tolerances in the cutting or manufacturing operations for producing the copy sheets often lead to irregularities in the actual dimensions of individual ones or batches of the sheets, thereby facilitating irregular stacking of the sheets in a given cassette.
During each copying or printing operation, copy sheets stacked in the cassette are individually fed by rotating feeding rollers brought into pressure contact with the uppermost sheet of the stack. In order to assure that only a single sheet is fed during this operation, it is known to lightly press the front corners of the uppermost sheet by so-called separation claws. However, when the stacked sheets are irregularly or incorrectly positioned or retained within the cassette--as, for example, at an angle or skew to the forward or feeding direction--uneven pressure contact exerted by each separation claw on the respective front corner of the uppermost sheet results, causing skewed feeding of that sheet. Skewed feeding of the uppermost sheet when the same is improperly positioned in the cassette is still further facilitated because the plurality of paper feeding rollers normally provided for paper feeding do not contact the sheet with equal pressure; one side of the sheet is consequently transported faster than the other, thereby contributing to the skew. The results of skewed feeding include production of copies wherein the image on the copy sheet is itself skewed, and the frequent occurrence of internal paper jams within the copying machine.
In seeking to avoid such skewed feeding of the copy sheets, it is known to provide extruded members of an elastic material--such as sponge or the like--on the interior walls of the cassette. However, because these members are so arranged that they are located at the same height and each exerts substantially the same contact pressure on copy sheets within the cassette along the full height of the sheet stack, they have not heretofore been effective in correcting transverse dislocations of cassette-held sheets. In addition, while these prior art arrangements have been somewhat successful in preventing skewed feeding of relatively wide copy sheets, they have been generally unsuccessful in avoiding skewed feeding of more narrowly dimensioned sheets.
In seeking to generally enhance business efficiency, high speed copying machines--and particularly those which function as direct output devices for document-generating computer apparatus--are being increasingly utilized. In such high speed machines, it is desirable to minimize necessary refilling of the cassette, and cassettes capable of retaining a relatively large number of copy sheets--for example, as many as 1,000 to 2,000--are known. Large capacity cassettes of this type are sometimes provided with a gate or opening vertically extending along the central portion of the opposed side walls to facilitate loading and unloading of copy sheets. Thus, an operator can grasp a stack of copy sheets along their central side edges and, while inserting the stack into (or removing it from) the high capacity cassette, reach into its interior through the side gates or openings.
Those skilled in the art will recognize that large capacity cassettes are considerably heavier as a result of their relatively increased size, and this becomes even more significant when such casettes are fully loaded with a supply of copy sheets. Although these cassettes are typically constructed of monolithically formed plastics having sufficient strength for normal use, they are subject to twisting about the side panel gates during loading of the cassette into the main body of a copying machine. Such twisting or deformation of the cassette structure often results in transverse shifting of either all or some portion of the stack of sheets contained in the cassette, thereby affecting subsequent sheet feeding during normal operation of the machine. Skewed sheet feeding is one important problem often resulting therefrom.